<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<script>

    //ES6 之后=============
    // 定义一个学生的类
    class Student{

        constructor(name){
            this.name = name;
        }

        hello(){
            alert('hello')
        }
    }

    class XiaoStudent extends Student{
        constructor(name,grade){
            super(name);
            this.grade = grade;
        }

        myGrade(){
            alert('我是一名小学生')
        }

    }

    var xiaoming = new Student("xiaoming");
    var xiaohong = new XiaoStudent("xiaohong",1);


</script>

</body>
</html>